Guidance and Control for Optimal Entry, Descent and Landing of Spacecraft
Guidance and Control for Optimal Entry, Descent and Landing of Spacecraft
SHEFEX II during re-entry
The artist's impression shows the re-entry of SHEFEX II into the Earth's atmosphere. Extremely high temperatures are generated at the tip of SHEFEX II at an altitude of between 100 and 20 kilometres at speeds of almost three kilometres per second.
Guidance and control (G&C) are critical subsystems for successful and reliable space missions. This is especially true for entry, descent and landing scenarios on Earth or other celestial bodies. Such missions involve multiple flight phases and speed regimes, requiring challenging multistage G&C designs. The guidance system must assure that constraints on the trajectory, induced by the vehicle or by environmental effects, are satisfied during flight. The design and development of such a G&C system requires a detailed analysis of the interaction between the spacecraft, the flight regime and the control algorithms.
During the last years multiple G&C systems have been developed for atmospheric entry for Earth and Mars, for lunar powered descent and for terminal vertical landing. The research focus is on the development of guidance systems that optimize the trajectory and control commands onboard in real-time. This is the basis for highly adaptive control systems with maximized operational domain, which at the same time achieve optimal performance. This is possible because constraints on the actuators and the states can be directly integrated into the control law. This is particularly important for autonomous systems that must operate based on uncertain assumptions or under a wide range of conditions. Some of these methods will be applied to ReFEx (Re-Usability Flight Experiment), a new entry vehicle developed by DLR, which is foreseen to be launched in 2019.
For testing G&C systems for vertical takeoff and landing the GNC Systems Department develops the demonstrator vehicle EAGLE (Environment for Autonomous GNC Landing Experiments). A corresponding safety-rig allows to test G&C algorithms with few preparations and in rapid iteration. This includes the profiling of the G&C software in the onboard real-time environment.
